Method for molding a nasal cannula

ABSTRACT

A flexible nasal cannula having improved characteristics is produced in a mold cavity incorporating a forming means comprising a transverse core having straight upper portions and a lower portion extending at an angle from the upper portion and a nipple core portion comprising a pair of rod-line extensions located toward the upper end of the upper portion and which extend substantially perpendicular to its axis. In a molding process, the forming means is maintained in spacial relation within a mold cavity, a thermoplastic material is flowed within the cavity around the forming means, cooled sufficiently to set the material and thereafter the cannula is removed from the forming means.

Aug. 6, 1974 H. R. HAVSTAD 3,327,926

mmaon FOR momma A NASAL cmmuu Original Filed March 22, 1971 FIG. 4

mm :MEIHODFOR MOLbINGA NASAL CANNULA arold R,;Havstad,=Lakewqod,1Calif.,assignor to apy Sales Co.

Ser. No. 126,452, now H nil, this application Feb.

1 Claim G en of application Ser. No. 126,452, a'r Z Z, 19 51, Pat.3,731,900.

BAOKGROUND OF -r- THE" "INVENTION m tly l eannula devices have becomevery important a a iiiefanjs'of administering oxygen to patients. Suchdevices are known to incorporate a flexible plastic tube h' h ced heupati'ent ',upper lip and main- A y an elastic strap or other rendingaroundthe patients head and s fjfith. plasticf tube. Such a device pai'rof extensions, usually referred to as nasa l tips which are hollow andjoin the plastic tube.

tips extend the patientfs nares or nasal pasa fibeflowsinto the maintube of patients nasal cavity andpharynx;

' Jen: incorporated into the canto improve their efliciency as ample'sof improved design tips c rved to conform to the ed fsurface' and/ orends which p" r lip and cheek respectively. patient comfort and maintheat'ient so that the nasal g therapeutic gases intro nited States PatentOflice 3,827,926 Patented Aug. 6, 1974 patient is unconscious orotherwise disabled to the extent of not being able to again insert thenasal tips into his nostrils, where a constant or necessary oxygensupply to the patient is absent, further injury could insue.

In order to eliminate cannula rotation caused by twisting of the oxygensupply tube, certain cannula devices have been improved by incorporatinghollow angled inlet tube which joins and extends from the main cannulatube and to which inlet tube an oxygen supply tube is attached. Such afeature is illustrated in US. Pat. No. 2,868,199. The use of an angledinlet tube, greatly reduces any rotational movement of the cannuladevice otherwise caused by the twisting of the oxygen supply tube. Thisfeature will be appreciated since any rotation or twisting of the oxygensupply tube will only tend to rotate the angled inlet tube but will notbe passed on to the main tube of the cannula which does not lie alongthe axis of either the oxygen supply tube or the angled inlet tube.Thus, the force of a twisted oxygen supply tube substantially terminatesat the angled inlet tube portion of the cannula.

In molding a nasal cannula of the type described above,

it has been the practice to use a plurality of forming means the"nasalfftips and directly into the 5 referred to as cores at least one ofwhich is retractable. Thus, separate cores are used in forming thetubular body portion of the cannula and the tube-like hollow nasal tips.Again, these cores are maintained in spacial relationship to the moldcavity within the closed mold while a thermoplastic material is injectedinto the cavity and around the cores. Thereafter, as the mold is opened,the cores around which the tubular body portion or the hollow nasal tipsare formed are retracted leaving the cannula remaining on theunretracted core. The mold operator thenpeels the cannula from the core.

In producing a cannula having a tubular main body about which thetubular main body is formed is referred to as a transverse core. Thecores used to form the hollow nasal tips are nipple cores. In the moldapparatus the transverse and nipple cores are brought together in anattempt to simulate a unitary or integral core at the phase during themolding process in which the material is injected into the mold cavityand around the cores. Thus, the nipple cores comprising two spaced rodswill meet and contact the transverse core so that when the injectedmaterial flows around these cores the hollow nasal extensions and hollowmain tube will join.

It will be appreciated that in attempting to produce a cannula in whichthe interior passageways for the flow of oxygen or other gases is to beunobstructed, i.e., flow along the main tube and through the nasal tips,the respective cores must be carefully machined so that no spaces arepresent between the nipple core and transverse core at the junctionarea. However, as the mold is used these cores become worn at theinterfaces and common points of contact. This wear due to friction andabrasion, results in small spacial areas being formed which in turn,allows for the injected material to flow in thesesrhallspaces.'Thismaterial which remains on the finished molded device is referred toas'fiash. Further, small diametercores are sometimes deflected bytheflowing thermoplastic produc- .1

ing" a deformed product, uneven interior and exterior surfacesand.flash... a, a e

Qnth e exterior o f-t'he cannula flash canbe trimmed to improvetheappearancepf the product; On, the other hand,

wherefiash 0 rs on thetinterior-l ofthe cannula andespev cia l ly= inthetubular orhollow -passageways ,'-cannula pen.

formancgcan be significantly. altered. Especially troublesome is flashlocated at the areas Wherethenasal tipsjoin the main: tube. It will beappreciated that significant amounts of flash at those areas willcauserestriction in the interior gas passageway and may greatlyreduce;the

. 3 amount of gas passing into either or both of the nasal tips andpossibly shut them off altogether. Accordingly, the avoidance of flashat the interior joinder areas of the hollow nasal tips and main cannulatube will be appreciated as will the disadvantages of using separatenipple and transverse cores.

In a well known and extensively used cannula device prepared by aninjection molding process, an angled inlet tube is present adjacent oneend of main cannula tube with the hollow interiors of cannula bodyportions communicating as previously described. In producing such adevice four separate cores are used: two nipple cores for forming thetwo hollow nasal tips, a transverse core for forming the hollow maintube and an angle core for forming the angled inlet tube. Thus, afurther problem of flash on the interior of the cannula device is causedwhere the angled inlet tube communicates with the main cannula tube,

thereby presenting the same problems of possible stoppage-v orinterruption of gaseous flow from the angled inlet tube into the maincannula tube as above noted for the nasal tips. Further, since thetransverse core used is substantially a straight rod, the main tube ofthe cannula has an open end when initially formed which must be pluggedso that only the nasal tips and angled inlet tube are opened to theexterior of the cannula device. The plugging of this opening is usuallyaccomplished by hand and obviously requires additional time and effortto complete the device which concomitantly increases production costs.

SUMMARY OF THE INVENTION In the cannula molding process of the presentinvention a unitary core is utilized having an angle core portion, anaxial transverse core portion and a nipple core portion each of whichportions are integral with and a part of the single unitary formingcore. In the injection molding process the unitary core is maintained inspacial relationship with the mold cavity, material is injected into thecavity around the core, the mold is opened and the cannula device isremoved from the core. Since the core is unitary in construction, noseparate cores are used thereby eliminating flash on the interior of themolded cannula device. The device is removed from the core and a lippedslot formed at the bridge where the core is attached to a core supportis closed by a radio frequency welding process. The unique forming meansor core described herein, in addition to eliminating interior flash,produces a cannula having hollow nasal tips, a hollow main tube and ahollow angled inlet tube. The device has no other tube openings whichmust be plugged as previously described except for the lipped slot whichis sealed and the lips removed. A further embodiment of the inventionutilizing multiple cores will be more fully described hereinafter.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 illustrates a cannula formingcore of the present DETAILED? DESCRIPTION OF THE INYENTION' Referring toFIG. 1, a forming core shown generally as 10 has an upper-portion 12, anangle portion 18 and nipple portions 14 and'15. These portions areintegral thus COlIl-f' prising the unitary forming core 10. The nippleportions 14 and 15 are separated rod-like extensions, one located'at'upper portion 12, and the or near the upper end 17 of the other somewhatlower.

The nipple portions 14 and 15 extend substantially perpendicular fromthe axis of "the upper portion 12. These nipple core portions 14 and15in are spaced apart and I cooperation with the mold cavity form thenasal tips of: the cannula during the molding process. Accordingly, thedistance between nasal tips desired for the cannula to be produced aredependent on the distance between the portions 14 and 15. The nipplecore portions 14 and 15 may be substantially straight or curved wherecurved nasal tips are desired. The length ofthese nipple portions 14 and15 may also be varied depending ontheintended length of the nasal tipsof the cannula, I

The angle portion 18"extends'directlyffromi the upper portion 12 at thejoinder area 19 of the upper portiori 12 opposite the end 17. The angleat which the angle-portion v 18 extends from the upper portion 12 may bevaried depending on the angle desired'forthfangledinlet tube of thecannula produced. Generally, angles between about 20 and about aresuitable with those betweenabout 30 and about 45 preferred. The lengthofthe angleportiona. 18 will also depend on the desiredlength of theangledinlet tube. V I 1 The core 10 is attached to a core support, notshown, by bridge member 54 which is preferably;,-flat ,and extends alonga side of the upper portion 12."1'he,location,of the 1 bridge member 54is shown as extending from the end 17 w of the upper portion to somewhatbelowqthe lower nipple. core portion 14, and opposite the nipple coreportions 14 and 15. The length of the bridge 54 is important since if itdoes not extend beyond the lower nasal core portion 14".; the cannulacannot be easily removed from the core, as will be more fully explainedhereinafter.

The location of the bridge"54"along the upper core portion 12 andrelative to the nipple 'core portions 14 and 15 may be varied somewhatdepending on the mold cavity and the length of the nipple core portions14 and 15. Again, as shown, the bridge 54 is preferably opposite thenipple core portions 14 and 15. In that location, as the cannula isremoved from the forming core 10, the nipple core portions 14 and 15 candirectly exit through a lipped slot of the cannula formed by the bridge54. However, the bridge 54 may join the upper portion 12 closer to thejoinder area as of the nipple cores 1,4 and 15 with the upper portion 12other "than as shown in H therefrom, separate transverse core 20,1nipple core' 's 24 and 25 and angle core 22' are shown. The nipple cores24 and 25 comprise rod-like extensions around Jwhich hollow nasal tipsof a cannula'are formed ina previously I used mold apparatus. Thetransversecore 20 forms the hollow main tube portions of a" cannulawhile the angle,

core 22 forms the hollow a ng 1ed inlet tube of the cannula. In acannula molding process using a state of the art core assembly as shownin FIG, 2, the individual coresff 22 and 26 are maintained in spacialrelationship within" a hollow cannula mold as thermoplastic material, isin.

jected into the mold cavity. Just prior to material injection, the endof the angle core 22 is brought into contact with the side of thetransverse core 29. Similarly, the rod,- like nipple core extensions 24and 25 contact the side of the transversejpore 20, Bash: iof the'l cores'20, '22, 24 and 25 are attached to separate eore supports and corej'fslides, not shown. When the cores 'a're brou ght into, poi, sition, thefluid thermoplastic isinjected intoijthe "mold cavity and around theseparate coresQThe thermoplastic is cured and the mold is opened.lluririglthe mold'ppe n' ing stroke, the transve" fromthe parting planeor part line of the mold lialve's'i we i et s j n tf." cylinder or otherretracting niea'ns'jlthe angle core -2 2 'is" then'retracte'd, and thenipple cores are brought forward The cannula which is attached to thenipple cores is then peeled off.

The core of the present invention shown in FIG. 1 eliminates therequirement of separate forming cores shown in FIG. 2 therebysimplifying the molding apparatus since only a single unitary core isused. However, even more important is the elimination of internal flashin a cannula produced by the core of the invention as previouslyexplained. Thus, by eliminating the assembly of separate cores 20, 22,24 and 25 which must contact in order to form the hollow interior of acannula, flash occurring around the areas of contact of the individualcores is avoided, thereby producing a superior cannula.

A cannula prepared by the use of the forming core of the invention isillustrated in FIG. 3. The cannula includes a hollow main tube portion32, hollow angled inlet tube 36 joining and extending at an angle fromthe main tube 32, and hollow nasal tips 34 and extending substantiallyperpendicular from the axis of the main tube 32. The hollow interior ofthe main tube 32 communicates with the hollow interior of tips 34 and 35and angled inlet tube 36.

An elongated portion 40, also part of the cannula body, terminates in aflattened end 39 while a similar flattened end 38 joins the exteriorwall of angled inlet tube 36 where the latter joins the main tube 32. Itwill be noted that the elongated portion and flattened ends 38 and 39lie generally along the axis of main tube 32. Each of these flattenedends 38 and 39 are for the purpose of maintaining the cannula in a fixedand comfortable position on a patient with the aid of an adjustableelastic strap, not shown, secured through openings 44 and on therespective flattened ends.

Referring to both FIGS. 3 and 4 the unitary forming core 10 (FIG. 4) isattached to a core support 52 by a bridge 54, which bridge incooperation with the mold cavity forms a lipped slot 48 having a lip 42.This slot 48 is simply an elongated opening which enables the removal ofthe cannula from the forming core. When the mold halves are separatedleaving the cannula formed on the unitary core, the cannula 30 is peeledfrom the core 10 by pulling the cannula in the area of the nasal tips 34and 35 away from nipple core portions 14 and 15. Accordingly, the nipplecore portions 14 and 15 are pulled through the slot 43 and parting lip42. Once the nipple core portions 14 and 15 clear the lip 42 the cannulais pulled downward off of core portions 12 and 18 respectively.Thereafter, the lip 42 of the cannula is removed by sealing means whichboth cuts the lip 42 from the cannula body and seals the slot along seam43 shown in FIG. 3. If necessary, any exterior flash may be trimmed fromthe cannula body. A strap is threaded through openings 44 and 45 of theflattened ends 38 and 39 and the cannula is ready for use.

It will be evident that the length of bridge 54 and in turn the lippedslot 48 should be suflicient to permit easy removal of the cannula fromthe core without exceeding the elastic limits of the thermoplasticmaterial. In other words, the lipped slot 48 should permit withdrawal ofthe nipple core portions 14 and 15 therethrough without undulystretching the cannula.

FIG. 4 illustrates a further embodiment of the invention utilizing aplurality of forming cores 10 shown in FIG. 1. The individual unitaryforming cores 10 are attached to a removable rack device 50. The rack 50comprises a primary rod 56 along which extend substantially evenlyspaced core support rods 52. Attached along one side of each coresupport rod 52 is a bridge 54 to which is attached the forming core 10.Such a bridge is preferably flat, and relatively thin. It is thepresence of the bridge 54 which causes formation of the lipped slot 48on the cannula as shown in FIG. 3 and previously described. Pins 58 fitinto recesses on a mold apparatus and hold the rack 50 in properposition or alignment until the mold is closed prior to injection ofthermoplastic material.

The rack 50 is itself of unitary construction. Its advantage is not onlyto enable the simultaneous formation of a plurality of molded cannuladevices but generally permits improved efliciency in a mold operation.For example, such a rack is removable from the cannula mold by simplydisengaging the pins 58 from cooperating mold recesses. This may be doneby hand or automatically during the phase when mold halves are opened oropening. Thus, an operator may then peel oil? the cannulae outside ofthe mold apparatus which is advantageous from both a conveniencestandpoint as well as for safety. Where two of such racks are used, asingle operator can remove and inspect cannulae while the other rack isengaged in the molding operation. Thus, speed is also facilitated insuch an operation.

Although the rack of FIG. 4 engages vfour forming cores any number maybe used depending on the construction of the mold apparatus and thecapacity of the machine used in the molding operation. Thus, theinvention is not limited to the specific device shown but mayincorporate fewer or more forming cores. Similarly, the rack mayincorporate equivalent features other than those specifically shown toachieve substantially the same results.

A variety of thermoplastic materials may be used in forming a cannulaaccording to the invention although polyvinyl chloride and polyvinylacetate are usually preferred. These as well as alternative embodimentswithin the purview of the invention will be evidentto those skilled inthe art.

I claim:

1. In a process for injection molding a nasal cannula having anelongated hollow tubular body and a pair of hollow nasal tips extendingtherefrom utilizing a mold cavity and forming means within said cavity,the improvement comprising the steps:

(a) forming the cannula on a unitary core having (1) an elongatedportion terminating at an upper and lower end for forming the tubularbody and having the shape of the nasal cannula body interior,

(2) a pair of relatively short rods spaced along the length of theelongated portion and extending therefrom, one of the rods beingadjacent said upper end, for forming the nasal tips, and

(3) a bridge for securing said core to a core support means said bridgeextending from approximately the upper end of said elongated portion tobelow the rods and forming a slot for removal of the cannula from saidunitary mold core;

(b) stripping the formed cannula from the core bypulling the nasal tipsfrom said short rods and 'removing the cannula. from said core through alipped slot formed on said bridge and extending along a portion of saidtubular body; and

(c) sealing the lipped slot.

References Cited CHARLES E. VAN HORN, Primary Examiner C. WESTON,Assistant Examiner US. Cl. X.R. l28206, 348*; 156-245; 249-63; 264-318,328, 334

Shockey 264-318 l j

